Last couple weeks my right hand is in severe pain every time I work on the PC for more than an hour.
...
Although changing the lifestyle or working environment would help, it is impossible to do so.
There might be a chance to do at least a small change - moving computer mouse from the left to the right side. I guess using the opposite side of the body for long term would somehow compensate past 13 years...
I was trained as a workstation risk assessor in 1994, after a colleague developed problems and didn't take the recommended actions. Eventually he couldn't do home improvements nor the washing up; he wasn't
too worried about those
However neither could he type nor drive a car - even after going to the US for an operation.
With that in mind, there is no way I am going to offer advice as to what you should do, unless I had personally observed you working. Be very aware that people are bad at observing how they themselves are behaving; an external observer is often necessary.
In particular, I worry about people using laptops as their main machine: the small keyboards cause you to have poor wrist positions, and the low screen causes neck problems. Those issues can and should be avoided with external keyboards, plus either an external screen or the whole laptop off the desk supported by a stand.
The course of action you appear determined to take will probably cause you to develop problems in your
other hand; both hands will be affected.
Now it is your choice as to what actions you do and don't take. But if I was you I would be doing
absolutely everything to avoid the problems getting worse.
In the UK the HSE regulations are very clear. Your manager
must personally ensure you have the right equipment to work safely, and also personally prevent you from working in a way that might harm you or another. If you persist, he must stop you by whatever means are necessary. If he does not, then you can sue your company
and your manager personally. His saying "I told him to stop" is insufficient defence.